The invention relates to converters (inverters, pulse or frequency converters) and to the driving of, for example, machines and is implemented in form of a device (circuit arrangement) or a method for feeding such a magnetically active operating means in the sense of a transformer, a motor/generator (more general: a machine). A driving arrangement is concerned with the regulation or control of said circuit arrangement.
High demands are made to electrically operated driving means as an example of “magnetically active”, electrically operable operating means, on the one hand, regarding the noise behavior and, on the other hand, regarding the dynamics of regulation provided by frequency converters and servo converters as inverters. These converters provide an alternating current generated by a high switching frequency which, in machines of high power of more than 10 kW to 30 kW and, in particular, in draft-ventilated motors, results in the occurrence of disturbing noise levels in the motors caused by feeding the converters at a too low switching frequency.
In order to avoid or at least reduce said noise levels, the pulse frequencies (=switching frequencies) of the inverters must be increased, which also increases the power loss in said inverters, if they are required to switch high load currents of the machines. This is implemented at a “high switching frequency” which may be higher than e.g. 8 kHz. If the inverters (converters) are switched at this frequency, the noise levels may be kept within acceptable limits at the cost of an increased power loss in the converters which consist of a plurality of branches each, wherein, mostly in three-phase machines having three magnetically active and electrically fed windings, a converter having three phases and adapted to said windings may also be used.
If highly dynamic driving means are used, e.g. linear motors or motors which are required to synchronize with a high speed of a belt or web moving past it, the high pulse frequency is not only useful for reducing the noise level, but is also required to enable realization of a fast current regulation of said highly dynamic driving means (as representatives of magnetically active operating means).
If this first or the second or the common goal is to be achieved today, high switching frequencies are inevitable in inverters which then, even at high output currents, lead to high switching frequencies and high cooling requirements. These high requirements are caused by the fact that the power semiconductors fulfilling the high switching frequency in the respective branches of the inverter are required to switch the high generator or motor load current of the machine at said high frequency so that the power semiconductors, transistors or IGBTs, have to be appropriately dimensioned and mounted accordingly in the cooling or for dissipating the produced heat.